Modelling of spontaneous adhesion phenomena in micro-electro-mechanical systems

An innovative approach for the numerical study of spontaneous adhesion (or stiction) phenomena in Micro-Electro-Mechanical Systems (MEMS) is proposed, based on the use of 3D Finite Element (FE) models. Stiction is a major reliability problem in MEMS which can completely destroy the normal mobility of parts which have the task e.g. to sense the external acceleration in micro-accelerometers or the rotation velocity in micro-gyroscopes. Capillary and van der Waals forces are first selected as the most important sources of stiction; subsequently, these forces are modelled in a simplified way in view of their introduction in a FE model. As a second important ingredient in the proposed modelling approach for spontaneous adhesion, rough surfaces are numerically generated by making use of suitably adapted algorithms originally developed for tribology studies. A complete 3D FE model for two rough surfaces which come at very short distances is thus built and various results showing the modelling capabilities are shown. A comparison with experimental results recently appeared in the literature is proposed.